Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “CENTRIFUGATION”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 235 records · Page 13Linked to original sources
PubMed1985

Isolation of human alveolar macrophages and lymphocytes from bronchoalveolar lavage fluid by centrifugal elutriation.

Cell populations obtained by bronchoalveolar lavage (BAL) from humans showed varying proportions of lymphocytes and macrophages, about 5% and 94%, respectively, in healthy controls (n = 12), and about 24% and 75%, respectively, in patients with sarcoidosis (n = 13). The present study was carried out to examine centrifugal elutriation as a means to obtain from human BAL fluids highly purified populations of viable cells, required for further biochemical investigations. After centrifugation of BAL fluids at 400 g for 5 min, cells were resuspended in Hank-Tris solution, loaded into a Beckman elutriator rotor (rotor speed 2800 rpm) and elutriated with Hank-Tris in approximately 10 min. Cells were collected at flow rates of 20 ml/min (fraction I), 32 ml/min (fraction II) and, after stopping the rotor, 80 ml/min (fraction III). Fraction I contained mainly lymphocytes, about 54% and 74% in controls and sarcoidosis, respectively. Fraction III consisted almost solely of macrophages, while fraction II contained mixed populations. Total cell recovery was about 74% and 55% in controls and sarcoidosis, respectively. Half of the missing cells were lost during centrifugation, the rest during elutriation. Cell viability was 85-90% after the first centrifugation. Following elutriation, the viability was found unchanged in fraction III, but decreased to about 50% in fraction I of controls. The decrease may be due to the accumulation of dead cells with decreased density in this fraction. The results showed that centrifugal elutriation is a highly suitable technique for the isolation of macrophages from human BAL fluids. Enriched lymphocyte populations may be obtained from sarcoid BAL fluids.

Bronchi↗
PubMed1979

Comparison of the aerodynamic size distribution of chain-like aggregates measured with a cascade impactor and a spiral centrifuge.

Several authors have suggested that chain-like aggregates fragment in the jets of cascade impactors and that the impactor consequently underestimates the median aerodynamic diameter and overestimates the geometric standard deviation (GSD). The aerodynamic size distribution of (Pu0.14U0.86)02.2 aggregates were measured simultaneously with two Mercer cascade impactors and a LAPS spiral centrifuge to investigate this problem. Although the median aerodynamic diameters were generally in good agreement, the impactor consistently measured higher values for the GSD than did the spiral centrifuge. Based on experiments in which losses in the centrifuge inlet were measured, it was concluded that the centrifuge had measured the aerodynamic size distribution more accurately than the impactor. Interception of chain-like aggregates on the first few impactor stages may have been the primary reason for the disparity between the impactor and centrifuge measurements.

Aerosols↗
PubMed1970

A cytological study of the centrifuged whole, half, and quarter eggs of the sea urchin, Arbacia punctulata.

While the ooplasmic components of centrifuged eggs of Arbacia punctulata do not stratify in homogeneous layers, we have obtained the following strata beginning with the centripetal end: lipid droplets, pronucleus, clear zone, mitochondria, yolk, and pigment. Whereas mitochondria may be found mingled with yolk bodies, we have never observed lipid droplets nor pigment bodies among any of the other inclusions. The so-called clear zone contains a heterogeneous population of inclusions: annulate lamellae, heavy bodies, Golgi complexes, and rod-containing vacuoles. The peripheral cortical granules of immature (germinal vesicle stage) and of mature eggs are not dislodged from the cortical ooplasm with the centrifugal force utilized. When the eggs are treated with urethane, prior to centrifugation, the cortical granules of mature eggs abandon their peripheral position. Further centrifugation of the initially stratified eggs produces nucleated and nonnucleated halves and the centrifugation of the halves results in quarters. The cytology of the halves and quarters is discussed. The halves and quarters have been activated with either sperm or hypertonic sea water. With the exception of the nucleated halves, we were unable to obtain plutei larvae from the other fractions (red halves and quarters). We believe that the lack of development of the various fragments is a function of the balance of particular inclusions necessary for differentiation.

Animals↗
PubMed2001

Enhanced efficiency by centrifugal manipulation of adenovirus-mediated interleukin 12 gene transduction into human monocyte-derived dendritic cells.

Transduction of dendritic cells (DCs) with genes encoding tumor-associated antigen or with other genes that enhance immune reaction has been theorized to be potentially useful for enhancing the efficiency of DC-based immunotherapy. However, gene transduction of DCs generated from human peripheral blood monocytes has been of limited use because of the low efficiency. Here, we report that the efficiency of in vitro adenovirus-mediated gene transduction into human monocyte-derived DCs can be dramatically enhanced by centrifugation. The best conditions for centrifugal gene transduction were determined to be as follows: 2000 x g at 37 degrees C for 2 hr at a multiplicity of infection (MOI) of 10 or greater. By this centrifugal method, approximately 88 and 70% of DCs were gene transducible at an MOI of 50 and 10, respectively. Functional analysis showed that DCs transduced with human interleukin 12 (IL-12)-expressing adenoviral vector under the optimal conditions of centrifugation stably produced IL-12 protein at high levels (8.1 ng/10(6) cells/48 hr). IL-12 gene-modified DCs (DC/IL-12) displayed a more mature phenotype than nontransduced DCs, as judged by decreased expression of CD1a and increased expression of CD83, B7.1 (CD80), B7.2 (CD86), and MHC class I and II molecules. DC/IL-12 showed a high phagocytic ability similar to nontransduced DCs and were significantly superior to control DCs in the stimulation of autologous and allogeneic T lymphocyte responses. The centrifugal transduction method with adenoviral vector might be useful for efficient generation of gene-modified DCs because it is very simple, highly efficient, reproducible, and not cytopathic. IL-12 gene-modified human DCs may be therapeutically useful as a good adjuvant in DC-based immunotherapy.

Adenoviridae↗
PubMed1987

Rapid diagnosis of invasive cytomegalovirus infection by examination of tissue specimens in centrifugation culture.

Two hundred eight tissue specimens from 81 patients were examined by centrifugation culture for the rapid diagnosis of invasive cytomegalovirus (CMV) infection. Results were compared with those obtained by both conventional viral cultures and histologic examination. CMV was identified by centrifugation culture in 52 (25%) specimens at 16 hours after inoculation, including 39 lung specimens and 12 gastrointestinal specimens. One additional esophageal specimen was positive (53 of 208 specimens; 25.5%) at 36 hours. In contrast, CMV was recovered from only 50 of these 53 specimens by conventional cell culture at a mean of 11 days after inoculation. Forty-three of the 208 specimens (20.5%) were positive for CMV when examined by histologic methods, including light microscopy and tissue immunofluorescence. All 43 were positive by centrifugation culture. Specimens that were positive by centrifugation culture but negative by histologic methods included three lung specimens and seven gastrointestinal specimens. The technic of centrifugation culture is more sensitive for diagnosis of invasive CMV infection by the examination of affected tissue than either conventional viral culture or histologic technics, including tissue immunofluorescence, and more rapid than conventional culture or routine histologic examination.

Antibodies, Monoclonal↗
PubMed1989

Morphology and fertilizability of zona-free hamster eggs separated into halves and quarters by centrifugation.

When mature hamster eggs were freed from their zonae pellucidae and centrifuged in a Percoll gradient, each egg was separated into a light half and a heavy half. Chromosomes remained in their original position during centrifugation, resulting in the production of light and heavy halves with and without chromosomes. When the eggs were treated with cytochalasin D (CD) and then centrifuged, the chromosomes moved to the centripetal pole and were extruded rapidly before each egg separated into halves or fragments. In the eggs without CD treatment, the density of cortical granules was reduced in the centripetal region of the egg. In those treated with CD, the density of the granules was reduced in both centripetal and centrifugal regions of the egg. Both light and heavy halves were fertilizable. There was, however, a notable difference between light and heavy halves. Most of the heavy halves supported development of sperm nuclei into pronuclei, whereas only few of light halves could do so, suggesting that most of light halves were lacking or deficient in materials necessary for the development of a sperm (male) pronucleus. When the light and heavy halves were centrifuged further, each separated into two quarters. The lightest quarter, which was almost totally devoid of organelles, was buoyant and very fragile. Spermatozoa could fuse with it, but the incidence of the fusion was low. In this quarter, the sperm nucleus could decondense, but could not develop into a pronucleus. This was in marked contrast with other three quarters in which sperm nuclei could develop into well-formed pronuclei.

Animals↗
PubMed1995

Enucleation by centrifugation of in vitro-matured bovine oocytes for use in nuclear transfer.

Nuclear transfer has the potential to produce large numbers of identical progeny. Current limitations of the technique are associated with the use of micromanipulation for the demanding enucleation and reconstitution procedure. With the overcoming of this limitation, increased numbers of nuclear transfer embryos could be produced. Centrifugation of bovine oocytes at 15,000 x g for 2 min resulted in the stratification of organelles within the cytoplasm which positioned the metaphase II spindle for enucleation. After removal of the zona pellucida with Pronase, the oocytes were centrifuged in a Percoll density gradient so that the oocytes were stretched apart to form cytoplasts and the metaphase II spindle was separated from the majority of oocytes. Enucleation by centrifugation efficiently produced a consistent population of enucleated cytoplasts from bovine in vitro-matured oocytes. The population of enucleated cytoplasts was enriched by exclusion of the cytoplasts that exhibited an extrusion cone containing metaphase II chromosomes 6 h after centrifugation. The enucleated oocyte cytoplasts were aggregated with blastomeres isolated from in vivo-collected morulae. The aggregated embryonic cells were electrofused to obtain nuclear transfer embryos that were placed into a sodium alginate false zona and were capable of cleavage and development in vitro. The development of nuclear transfer embryos produced through use of centrifugation and aggregation techniques was comparable with that of nuclear transfer embryos produced by micromanipulation techniques.

Alginates↗
PubMed1986

Differential centrifugation of leucocytes and platelets applied to 111In-leucocyte labelling.

Platelet contamination of 111In-leucocytes can be minimized by centrifugation of leucocyte-rich plasma before labelling. The differential recovery of leucocytes and platelets from centrifugation depends on various biological and physical factors. Experimental measurements have been made of the effect of some of these factors. The ratio of leucocyte-to-platelet recovery was increased by using more than one centrifugation, and by using a low relative centrifugal force (RCF). To extend the study, a method of calculating cell recovery from centrifugation was developed, based on the experimental results. Calculations indicated that this ratio was at a maximum at around 85g RCF, and was least affected by changes in the suspension medium viscosity. At 85g, leucocyte recovery was incomplete, but calculations indicated that there was a preferential recovery of granulocytes which was subsequently verified by experiment.

Blood Platelets↗
PubMed2005

Hemolytic characteristics of three commercially available centrifugal blood pumps.

OBJECTIVE: As compared with traditional extracorporeal roller-occlusion blood pumps, nonocclusive centrifugal pumps offer the benefits of requiring a smaller circuit surface area and, thus, a smaller prime volume. However, centrifugal blood pumps have been reported to generate unacceptable levels of hemolysis. We hypothesize that the newer generation centrifugal pumps have an incidence of hemolysis similar to the traditional roller head pumps and, thus, could be used for extracorporeal membrane oxygenation circuits. DESIGN: Randomized, prospective, bench study. SETTING: University research laboratory. INTERVENTIONS: Three centrifugal blood pumps (Cobe Revolution, Jostra Rotaflow, and Medtronic BioMedicus) were compared with a roller occlusion blood pump (Cobe Century). Hemolysis generation was examined during 6 hrs of continuous use. Two test runs per group were randomly performed on three consecutive days for a total of six test runs for each of the four pumps (n = 24). MEASUREMENTS AND MAIN RESULTS: Plasma free hemoglobin values were determined using a Spectra MaxPlus spectrophotometer. A normalized index of hemolysis was calculated to compare the individual trials. The Cobe Revolution and the Jostra Rotaflow compared favorably with the Cobe Century roller occlusion blood pump in the amount of hemolysis produced. CONCLUSIONS: These data are encouraging for the development of a low-prime, mobile neonatal extracorporeal membrane oxygenation circuit using centrifugal pump technology.

Animals↗
PubMed1986

Column centrifugation generates an intersubunit disulfide bridge in Escherichia coli F1-ATPase.

Passage of F1-ATPase through a centrifuge column [Penefsky, H. S. (1979) Methods Enzymol. 56, 527-530] caused formation of a product with a relative molecular mass of 72,000 as determined by sodium dodecyl sulfate/polyacrylamide gel electrophoresis. The product was identified as cross-linked alpha and delta subunits by using Western blots and subunit-specific monoclonal antibodies. The cross-link was reversed by 50 mM dithiothreitol implying that it was a disulfide bridge. Formation of the cross-link was inhibited by 2 mM EDTA and was stimulated in some buffers by the addition of 10 microM CuCl2. Time course experiments indicated that the majority of the cross-link formed while the enzyme was passing through the column. Thus the cross-link induced by column centrifugation arose from the rapid, heavy-metal-ion-catalysed oxidation of two sulfhydryl groups, one on the alpha subunit and one on the delta subunit, to a disulfide. These results demonstrate that care must be exercised when running proteins through centrifuge columns as potentially deleterious disulfide formation can result. An anti-beta monoclonal antibody was capable of immunoprecipitating the entire enzyme including the cross-linked subunits, implying that the cross-linked alpha and delta subunits were still a part of F1. The formation of the cross-link affected neither the hydrolytic activity of the enzyme nor its susceptibility to inhibition by epsilon subunit. The cross-linked enzyme was unable to bind to F1-depleted membranes in experiments in which soluble F1 and membranes were separated by centrifugation. Column centrifugation did not generate the cross-link on membrane-bound enzyme. These results indicate that the alpha-delta cross-link results in a loss of binding affinity between F1 and F0.

Antibodies, Monoclonal↗
PubMedDate not supplied

Effect of multiple centrifugations on the evaluation of the acrosome reaction in human spermatozoa.

This study was undertaken to assess the effect of multiple centrifugations on the human acrosome reaction and in vitro fertilizing ability. Semen samples were obtained from sperm donors and from patients participating in our in vitro fertilization programme. Measured sperm samples were centrifuged twice (400xg for 5 min) before or after the induction of the acrosome reaction with calcium ionophore A23187 and before the insemination of oocytes. The samples obtained from the sperm donors were used to measure the acrosomal loss by means of indirect immunofluorescence (T6 monoclonal antibody) and the patient samples were used to assess fertilizing ability and cleavage. Samples centrifuged twice before the chemical induction of the acrosome reaction exhibited significantly elevated levels of acrosomal loss (mean = 46%) as compared to the controls (23%). However, the fertilization (P = 0.688) and cleavage (P = 0.187) rates were not significantly different between the controls and the centrifuged samples. The present study has shown that the centrifugation of motility enriched (swim-up) samples may also modify the acrosomal membrane complex, without compromising fertilizing potential.

Acrosome↗
PubMed1997

Effect of centrifugation on the pressure resistance of exponential phase cells of Escherichia coli 8164.

Exponential phase cells of Escherichia coli NCTC 8164 that were centrifuged at 2000 g for 20 min at 4 degrees C were more resistant to subsequent pressure treatment than cells grown in trypticase soya broth (TSB) and treated without any centrifugation steps. The effects of mild pressure stress (200 kPa for 20 min) and temperature stress (a shift from 37 degrees C to 4 degrees C) involved in the centrifugation procedure were analysed separately. It appeared that the increase in pressure resistance obtained following centrifugation was mainly due to the gradual temperature decrease during centrifugation, while the mild pressure stress seemed to play a smaller role in the response.

Centrifugation↗
PubMed1989

The physics of continuous flow centrifugal cell separation.

The governing equations defining the separation of blood in continuous flow centrifuges are derived using an empirical model for the viscosity of blood. The effects of fluid shear on the separation process are addressed and further models are developed to permit estimations of shear rate during centrifugation. Simplified predictive equations for species specific separations are developed. Contributions due to shear enhanced diffusion are addressed and found to be negligible at the discontinuous interface between cells and plasma. Experimental results from an investigational centrifuge are presented and compared with theoretical predictions. The role of rouleaux formation in conventional centrifuges is discussed and known centrifugal separation characteristics are explained. The viscosity of blood is related to that for suspensions of rigid particles and an equation for the hydraulic permeability of red blood cell suspensions is derived.

Blood Component Removal↗
PubMed1996

Modification of a pivot bearing system on a compact centrifugal pump.

The pivot bearing centrifugal blood pump was developed as a long-term centrifugal ventricular assist device (VAD) as well as a cardiopulmonary bypass pump. This pivot bearing supported centrifugal pump with an eccentric port (CIE) incorporates a seal-less design with a blood stagnation-free structure. This pump can provide flows of 12 L/min against 650 mm Hg total pressure head at 3,600 rpm, and in a CPB condition 5 L/min against 350 mm Hg total pressure head at 2,600 rpm. Very recently, the pivot bearing system was modified to obtain a stable and smooth spinning movement. The material of the female pivot was changed from ceramic to polyethylene. Three kinds of bearings were tested simultaneously with bovine blood in two types of in vitro circuits to determine the blood damage from the bearings. Pressure differences across the pump (total head pressure, delta P) of 140 mm Hg (n = 12) and 330 mm Hg (n = 12) were examined. The normalized index of hemolysis (NIH) was slightly higher in a ball bearing (BB) pump than in a polyethylene bearing (PB) pump and statistically higher than the BioMedicus Pump (BP-80) on delta P of 140 mm Hg. When the delta P was at 330 mm Hg, a comparison between the three types of pumps revealed no difference in NIH. In addition, the primary vane of the impeller was redesigned to obtain an atraumatic structure. In the second study (n = 14), there was no difference in the NIH between BP-80 and the current model when the delta P was 300 mm Hg (0.019 +/- 0.002 vs. 0.027 +/- 0.006, p = 0.3) and/or when the delta P was 100 mm Hg (0.0008 +/- 0.0001 vs. 0.0014 +/- 0.0002, p = 0.07). The modified pivot bearing had an improved spinning condition and no change in hemolysis. A proper selection of pivot bearing materials is important to develop an atraumatic centrifugal pump. The modification of the bearing system and redesign of the vane enabled a compact centrifugal pump to become a reality.

Animals↗
PubMed1997

Hemolysis in different centrifugal pumps.

Different types of centrifugal pumps cause different amounts of hemolysis based on shear stress and blood exposure time. However, the hemolytic characteristics of centrifugal pumps in each clinical condition are not always clear. We compared the hemolytic characteristics of one cone-type centrifugal pump (Medtronic BioMedicus BP-80) and 2 impeller-type centrifugal pumps (Nikkiso HMS-12 and Terumo Capiox) under experimental conditions simulating their use in cardiopulmonary bypass (CPB), extracorporeal membrane oxygenation (ECMO), and percutaneous cardiopulmonary support (PCPS) as well as their use as left ventricular assist devices (LVADs). The normalized indexes of hemolysis (NIHs; grams free plasma hemoglobin per 100 L blood pumped) during use as LVADs were not significantly different among the 3 pumps. The BP-80 pump produced almost 3-fold more hemolysis than the HMS-12 and Capiox pumps during CPB, 3- to 4-fold more hemolysis during ECMO, and 5.5-fold more hemolysis during PCPS. The 2 impeller-type centrifugal pumps will therefore cause less hemolysis under high flow, high pressure difference (as in CPB) and low flow, high pressure difference (as in ECMO and PCPS) conditions than the cone-type pump.

Animals↗
PubMed2004

Modeling centrifugal cell washers using computational fluid dynamics.

Reinfusion of shed blood during surgery could avoid the need for blood transfusions. Prior to reinfusion of the red blood cells, the shed blood must be washed in order to remove leukocytes, platelets, and other contaminants. Further, the hematocrit of the washed blood must be increased. The feasibility of using computational fluid dynamics (CFD) to guide the design of better centrifuges for processing shed blood is explored here. The velocity field within a centrifuge bowl and the rate of protein removal from the shed blood has been studied. The results obtained indicate that CFD could help screen preliminary centrifuge bowl designs, thus reducing the number of initial experimental tests required when developing new centrifuge bowls. Although the focus of this work is on washing shed blood, the methods developed here are applicable to the design of centrifuge bowls for other blood-processing applications.

Blood Component Removal↗
PubMed1991

Sedimentation of a suspension in a centrifugal field.

To model centrifugal sedimentation of biological suspensions, the time history of sedimentation of particles in a centrifugal field was considered for two geometries: a tube and a cylindrical container. The Kynch theory for batch gravitational settling in Cartesian coordinates based on mass conservation was extended to include a centrifugal sedimentation force, cylindrical coordinates, and the Hawksley-Vand hindered settling model. The resulting quasi-linear partial differential equation was solved by the method of characteristics. The combination of radial dependence of the sedimentation force and cylindrical geometry in the centrifugal case results in several differences in the time-position history diagram of the sedimentation process compared to the gravitational case. First, instead of a region of uniform concentration equal to the initial concentration, a region of concentration that is continuously decreasing with time results. Second, in the region of particle accumulation, curved constant concentration contours result instead of straight lines. Finally, a secondary shock that is dependent upon the initial concentration and the radius ratio of the rotating vessel appears in the centrifugal case. The time history of the concentration for a particle suspension with an initial concentration typical of blood is presented.

Blood Sedimentation↗
PubMed1995

[Basic and clinical evaluation of lysis centrifugation in candidemia].

Basic and clinical evaluation of lysis centrifugation using Isolator 10 was performed and compared with culture bottle methods. Blood, which was inoculated with C. albicans, C. tropicalis or C. parapsilosis, was cultured using lysis centrifugation or culture bottle method. The culture duration of C. albicans and C. parapsilosis by lysis centrifugation was shorter than that by the culture bottle (BHI release). C. albicans, C. parapsilosis and C. tropicalis became culture-positive within 1 or 2 days after culture by lysis centrifugation. C. albicans and C. parapsilosis became positive 4 days and C. tropicalis 6-8 days after culture by the culture bottle (BHI super). Clinical evaluation of both blood culture method as performed from April 1990 to March 1994. Sixty samples (4.4%) were positive out of 1370 samples. Twenty eight samples (7.2%) were positive out of 389 samples, which were examined by both methods. Twenty two samples were positive by both methods and the rest of the 6 samples was positive only by Lysis centrifugation.

Blood↗